Telephone system



Nov. 22, 1938. H 'QARG 2,137,626

TELEPHONE SYSTEM Filed NOV. 25, 1935 fzfezzzzmv A Herma/7n Marg @Y @GWWPatented Nov. 22, 1938 UNITED STATES PATENT OFFICE TELEPHONE SYSTEMApplication November 23, 1935, Serial No. 51,243 In Germany November 27,1934 13 Claims.

The invention relates to telephone arrangements of the type known asprivate branch exchange systems, and more lparticularly to arrangementsof this kind having one remote extensionstation and a main stationbetween this and the exchange, and it has for its object to aiord theextension station unrestricted automatic traffic with the main stationas well as with the exchange. This is attained through A`switching meanswhich, iniiuenced in a dierent manner vby the extension station and overits two wire line, selectively effect the automatic ringing of theexchange or the transmission of ringing current to the main station.

An incorporation of the invention is described hereafter with referenceto the accompanying drawing that diagrammatically shows the circuitarrangement of the main station HSt and of the remote extension stationNSt as well as a relay Abank RS comprising a repeating coil Ue. Thisbank, for instance can be arranged in a cabinet at the station HSt.Station NSt has a dial D of any well-known construction.

Relays are denoted by capital letters, their contacts by the respectivesmall letters.

The arrangement operates as follows:

Incoming exchange calls If a call `comes in from the exchange over lineAL, call relay AR operates so as to actuate Yringer G:

Relay HR operates:

ground, HU, hI, aIlI, 12h11, NU', HR/resistance (HRI), resistance(I-IR2) wIV, arIr, Wil,

and holds over its Vcontact hrII.

In order to answer a call, the operator at the main stationHSt lifts.the receiver, so that switch hook HU operates, and presses lockingexchange key AT. 'This establishes a direct connection of the exchangeline with the talking device of the main station. The talking deviceconsists of repeating coil J, receiver F, and transmitter M. By removingthe receiver the circuit for relay HR is broken at the lowest contact ofthe switch hook HU.

Intermediate-call from the main, station to the etensiofn station tion,for instance, it is necessary to operate key AN at the main station. KeyAN locks mechanically and releases exchange key AT. However,intermediate-call spring assembly Rf remains actuated, so that theexchange line is held over Rf and Wz'2. 'I'he extension station is nowcalled by means of key NRT. Relay R operates and at its contact rII itcloses the circuit o'f relay interrupter P, so that alternating currentis transmitted to the extension station over contacts rI'II and TI aswell as over contact pV. After lifting the receiver the extensionstation is fed over supply bridge A, X.' This supply bridge serves atthe same time the purpose of feeding the main station. Both stations arenow connected with each other over the contacts of An, rest contacts uI,uIII and TI, rIII. Since a `local call is involved, a damping resistanceWz'3 lies in the intermediate-call circuit.

If the main station wishes to end an intermediate-call connection, keyAT has to be pressed again, whereby key AN is released. The main stationis thus connected again with the exchange. If the hand set has also beenreplaced at the extension station, the supply lbridge will break down.

Taking over of an exchange call by am. extension station After the mainstation has informed the extension station through an intermediate-callthat an exchange call is Waiting, the latter station can take over theexchange call vby operating 'a grounding key ET. ADifferential relay Xis thereby energized and relay U is caused to-operate:

-, UI, hIII, 01V, -l-

Relay V is energized:

-, (V), V, aI, ull, -l-

At contacts uI and uIII extension line NL is connected with repeatingcoil Ue and the intermediate-call circuit Q, NL of the main station isbroken. The secondary Vwinding of the repeating -coil Ahas been:connected with the exchange line over vIV, all, oVI and oV,consequently the talking connection between the extension station andthe exchange has been established. By thevpressingof grounding key ET onthe part of the vextension station,` ringer G is caused to operate:

so that the main station will receive an audible signal `of .the takingover of the call. If the grounding key is released at the extensionstation, relay X returns to its rest position, so that ringer G willstop ringing. Furthermore, relay H operates:

H, vnr, U11, uv, xv,

The short circuit of Visible signal SZ is removed at contact hII, sothat, after replacing the hand set, that is to say after opening thecenter contacts of HU, it becomes evident at the main station that theexchange line has been seized by the extension station. On replacing thereceiver. exchange key AT is automatically released.

Call back from the etension station to the main station If key ET isoperated at the extension station, relay X will operate as has alreadybeen described. Holding winding II of U is open-circuited at :EV inorder to cause U to release. At aI and uIII the extension station isswitched off from the repeating coil Ue and thereby from the exchangeline and is switched over to the call back line Q of the main station.Relay H remains energized over :nV until, after the release of thegrounding key, relay X releases. After the release of relay H, theexchange line is held over hV and 22V; also winding VBI of relay VB isenergized over aIII, hI, HU and ground.

In order to call the main station, the extension station will turn itsdial from any digit onward. Relay A will release in the rhythm of thedial. After the first release of relay A, winding I of relay W isenergized over vbII. Every time that relay A is now caused to operate,ringer G will ring over aIII, wIII and NU" and thereby the main stationis called in the rhythm of the dial interruptions. The receiver isremoved at the main station and exchange key AN is operated, so that thetalking device of the main station is connected with the extensionstation.

When the intermediate call is ended, key ET has to be operated oncemore, so that relays X and U will operate. After releasing the key andafter the release of X; H is also energized again. The extension stationis thus as before again connected with the exchange. The talking deviceat the main station has to be restored.

Exchange calls from the extension station After lifting the hand set atthe extension station, grounding key ET has to be operated. Relays X andU in the relay bank are thereby actuated. Relay V also pulls up. Afterreleasing the key, relay X is caused to release and H pulls up. As soonas the exchange signal sounds, the transmission of impulses can bestarted. Contact aII transmits the dial impulses, which are received byrelay A. During the rst release of relay A, the short circuit forwinding II of relay VB is interrupted by contact aI, so that this relayre-Y mains switched over during the entire series of impulses and thatit short-circuits those windings of repeating coil Uel at vbI, which areshown on the left, in order to assure a faultless transmission ofimpulses to the exchange. After each series of impulses, relay VB isagain caused to release at aI through a short circuit.

If the hand set is restored at the extension station, A is deenergizedand the exchange loop is opened at aII. aI causes V to release through ashort circuit and UII causes relay VB to be deenergized. Contact vIIIswitches off relays U and H, so that the exchange line is released.

Calling of the main station by the extension station After lifting thehand set at the extension station, relay A pulls up. Over its winding Irelay VB is energized over ground, HU, hI, aIII, The dial D is nowturned from any desired digit onward, so that winding I ofrelay W isenergized over aIII and vbII. Now ringer G of the main station isoperated over ground, HU, hI, aIII, wIII, NU

in the rhythm of the dial impulses. If the main station does not answer,it is called again by repeated dialing. Relay W returns to its restposition after each series of impulses and it switches oif the ringer atwIII. By lifting the receiver and pressing key AN, the main station isconnected with the extension station. Both instruments are supplied overthe windings of relays A and X.

During the night, night switch NU, NU', NU" l of the main station isswitched over. When an exchange call comes in, relay Ris energized l,

over

ground, arIII, wV, NU

This relay connects pole changer P at rII, so that the extension stationis called indirectly. After lifting the hand set at the extensionstation, key

ET must be temporarily operated, whereby relays X, U, V and H are causedto operate in the described manner. After releasing the key, theextension station is in connection with the exchange subscriber.

Automatic transfer of the exchange call If it has been forgottentoswitch the night switch NU, NU', NU, then with the incoming of anexchange call relay HR is energized:

ground, HU, hI, aIII, UbII, NU', HR/(HRI), re-

sistance (HB2), wIV, arI, Wil,

Relay HR holds over hrII. Hot wire relay Hi is` connected at hrI. Sincethe main station does not answer, the hot wire relay will throw over itscontact after l5 to 20 seconds and over hrIII it causes relay W to pullup over its second winding. W holds over i wII, NU', '01311, aIII, hI,HU, ground In the next ringing current period relay R is energized overground, arIII, wV, vbVI,

and the extension station is called, as already described, by means ofpole changer P. If the extension station doesl now answer, relay A willoperate, relays W and HR being thereby thrown off through aIII. If keyET is now operated, then the extension station is in connection with theexchange subscriber.

The extension station does not answer W to release through a shortcircuit over hrIII. 75 1 Listening in 'Dverscondensers1Cl., C2 the mainstation vis in a position to .listen in on exchange calls ,of theextension station, and over condensers C3, C4 the extension station maybe Aenabled to listen in on calls `of the main station, in case this isdesired.

What is claimed is:

1. In a telephone system, an exchange, a main telephone station, a lineconnecting said main station and said exchange, a subordinate station, atwo-wire line connecting said subordinate station and said main station,switching means associated with the main station adapted for causing theactuation of a call signal at either the exchange or the main station, afirst means at said extension station for applying a ground to said linewhile leaving said line otherwise intact to actuate a call device onlyat said exchange, and separate means at said extension station forcausing a periodically interrupted current to flow serially through bothWires of said line to actuate a call device only at said main station.

2. A telephone system according to claim 1, further comprising means forestablishing an intermediate-call connection between the extensionstation and the main station during the existence of a connectionbetween the exchange and the extension station, said means being underthe control of the said switching means.

3. A telephone system according to claim 1, wherein the means fordiscriminatively influencing said switching means comprises a device forgrounding the two-wire line and a device for interrupting this lineperiodically, which comprises at the main station means, controlled bythis grounding device, for initiating a call-back connection and meansgoverned by said lineinterrupting device for transmitting ringingcurrent to the main station.

4. A telephone system comprising an exchange, a main station, anexchange line connecting said exchange and said main station, a mainstation telephone associated with said main station, an extensionstation, a two-wire line connecting said extension station and saidlmain station, an extension telephone associated with said extensionstation, switching means at said main station alternatively operable toestablish a connection between said extension telephone and saidexchange line or to initiate a call from said extension telephone tosaid main station telephone, selectively operable means associated withthe extension station for selectively controlling said switching meansover said two-wire line, and means for maintaining in nonoperativecondition an exchange connection established between said exchange andsaid extension telephone and for initiating a call between saidextension telephone and said main telephone responsive to actuationcfsaid selectively operable means while so maintaining said exchangeconnection.

5. A telephone system comprising an exchange, a main station, anexchange line connecting said exchange and said main station, a mainstation telephone associated with said main station, an extensionstation, a two-wire line connecting said extension station and said mainstation, an extension telephone associated with said extension station,switching means at said main station operable tol answer a call fromsaid exchange, means to establish a connection between said mainvstation telephone and said extension telephone while maintaining saidexchange line in answered condition, and selective switching means atsaid main station for establishing a connection between said extensionstation and said answered exchange line while maintaining saidv,exchange line answered responsive to a signalreceived from saidextension station.

6. A telephone system comprising an exchange, a main station, anexchange line connecting said exchange and said main station, a mainstation telephone associated with said main station, an extensionstation, a two-wire line connecting said extension station and said mainstation, an extension telephone associated with said extension station,switching means at said main station operable to answer a call from saidexchange means to establish a connection between said main stationtelephone and said extension telephone while maintaining said exchangeline in answered condition, selective switching means at said mainstation for establishing a connection between said extension station andsaid answered exchange line while maintaining said exchange lineanswered responsive to a signal received from said extension station,and means for giving an indication at said main telephone in response tothe reception of said signal from said extension station.

7. A telephone system according to claim 1, comprising a supply circuitfor the extension station, and a visual signal at the main stationincluded in this circuit in order to indicate to thev main station thatthe exchange line is busy.

8. In a telephone system according to claim l, an arrangement forestablishing a call back connection from the main station to theextension station, and an arrangement for establishing a call backconnection from the extension station to the exchange, the call backline of the latter arrangement being a by-path by which the call backline of the former arrangement is passed around.

9. A telephone system according to claim 1, which further comprises aswitch at said main station which is adapted upon actuation to leadincoming exchange calls directly to the extension station.

10. In a telephone system according to claim 1, a switch associated withthe main station and adapted upon actuation to lead incoming exchangecalls directly to the extension station, an interrupter, means forstarting this in response to an incoming exchange call, and means fortransmitting ringing current from this interrupter to the extensionstation.

1l. In a telephone system according to claim 1,

a switch associated with the main station and adapted upon actuation tolead incoming exchange calls directly to the extension station, aninterrupter, means for starting this responsive to incoming exchangecall means for transmitting ringing current from this interrupter to theextension station, means enabling the main station to originate a callback connection, and provisions for transmitting ringing current fromsaid interrupter to this call back connectiton.

12. In a telephone system according to claim 1, a switch associated withthe main station and adapted to lead incoming exchange calls directly tothe extension station, an interrupter, means for starting this by anincoming exchange call, a timing switch, means for energizing saidtiming switch in response to an incoming exchange call, said energizingmeans being adapted to be cut out by the said switch, and means,governed by said timing switch, for transmitting ringing current fromsaid interrupter to the extension station.

1S. In a telephone system according to claim l,

a switch associated with the main station and.

adapted to lead incoming exchange calls directly to 'the extensionstation, an interrupter, means for 10 starting said interrupter by anincoming ex- HERMANN QARG.

